Controllably self-releasable safety fastener and method of unlocking same

ABSTRACT

A safety fastener with controlled automatic release upon occurrence of given critical outside influences, with means for sensing and transducing at least one force applied to at least one fastening element, comprising means for integrating with respect to time the signal from the sensing and transducing means, means for comparing this signal with a given least reset value for the integrating means when the signal is below this least value, means for comparing the signal integral to a given maximum value and fastener-unlocking means operated when the integral is above said given maximum value.

United States Patent Lautier et a1.

1 1 Nov. 11, 1975 CONTROLLABLY SELF-RELEASABLE SAFETY FASTENER ANDMETHOD OF UNLOCKING SAME Inventors: Dominique Jean Lautier. Jouy enJosas'. Lucien Louis Maeder', Pierre Edmond Mayer, both of Paris, all ofFrance Agence Nationale de Valorisation de la Recherche (ANVAR), Neuillysur Seine. France Filed: Apr. 8, 1974 Appl. No: 458.590

Assignee:

Foreign Application Priority Data Apr. 10. 1973 France 7312931 US.Cl....... 307/119; 280/1135 M. 340/248 A Int. Cl.'- A63C 9/00 Field ofSearch 307/119. 324/130. 76 A; 340/248 A; 280/1135 M. 11.35 T. 11.35 A.11.35 D

156] References Cited UNlTED STATES PATENTS 3.105.231) 9/1963 Maclnqre324/130 UX 3.559.788 1/1971 Jensen 307/119 X 3.587.078 6/1971 Eichmann340/248 A 3.671.054 6/1972 Mittelstadt 2811/1135 M PrimaryExaminer-Herman Hohauser [5 71 ABSTRACT A safety fastener withcontrolled automatic release upon occurrence of given critical outsideinfluences. with means for sensing and transducing at least one forceapplied to at least one fastening element. comprising means forintegrating with respect to time the signal from the sensing andtransducing means. means for comparing this signal with a given leastreset value for the integrating means when the signal is below thisleast value. means for comparing the signal integral to a given maximumvalue and fastener-unlocking means operated when the integral is abovesaid given maximum value.

27 Claims, 18 Drawing Figures U.S. Patent Nov. 11,1975 Sheet 1 of63,919,563

Sheet 3 of 6 Nov. 11, 1975 US. Patent U.S. Patent Nov. 11, 1975 Sheet 4016 3,919,563

U.S. Patent Nov. 11,1975 Sheet5of6 3,919,563

w W R gm tfa Sheet 6 of 6 3,919,563

US. Patent Nov. 11, 1975 LEM.

CONTROLLABLY SELF-RELEASABLE SAFETY FASTENER AND METHOD OF UNLOCKINGSAME The present invention relates generally to a controllablyself-releasable safety fastener device or like latch contrivancc withautomatic controlled or controlresponsive release or like self-actingactuationresponsive or operated opening comprising means for locking amember to be released upon the occurrence or under the action ofpredetermined critical outside or extraneous influences as well as to amethod or process of unlocking such a fastener or latch.

This kind of fastener and this method of unlocking may be used in manyfields such as automative engineering, automobile vehicles and cars,aviation and aircraft every time securing devices are used for locking amember adapted to be automatically and controllably or operativelyopened or released by the occurrence or under the action ofpredetermined critical extraneous influences. In particular the fasteneraccording to the invention may be a safety binding appliance or likesafety attachment means mounted on a ski and normally enabling to lockor secure the boot or shoe of a ski-runner and to release, free ordisengage same upon the occurrence or under the influence of criticalextraneous influences such as the force exerted upon the foot or leg ofthe ski-runner when a fall happens.

Already known safety bindings for skis work unsatisfactorily as on theone hand they are opened or released too slowly in case of very heavyand short shocks and on the other hand they are not very faithful orthey show little fidelity, i.e. they are not caused to be released inevery case for the same magnitude or strength of force.

The principle of operation of these prior art fasteners consistsgenerally in measuring a force or torque exerted upon an element of thefastener and comparing the value of the measurement with a predeterminedmaximum value for triggering or not the release or opening of thefastener. This principle is wrong since it necessarily assumes that itis the forces applied on the foot or leg of a ski-runner which are thecause of the fractures of bones. On the contrary, it has become apparentthat the fractures of the bones are brought about by the integral withrespect to time of the forces applied, i.e. by the momentum or impulseapplied to the foot or leg of the ski-runner,

Another inconvenience of the known prior art fasteners is the fact thatin general the release devices are mechanical tripping or disengagingdevices exhibiting little fidelity and high inertia the power source ofwhich is the inertia of the skirunner himself.

In order to avoid all these disadvantages the invention provides asafety fastener with controlled automatic release or opening operatedupon the occurrence or under the action of predetermined criticalextraneous influences, including means for sensing or detecting andtransducing at least one force applied to at least one element of thefastener and characterized in that it comprises means for integratingwith respect to time the signal output from the sensing and transducingmeans, means for comparing the magnitude of this signal to apredetermined minimum valve and for resetting the integration means whenthe signal is below this minimum valve, means for comparing the signalintegral to a predetermined maximum value and fastener unlocking meansactuated when the integral is above said maximum value.

Thus the fastener according to the invention actually uses the momentumthat the foot or leg of the skirunner has undergone directly orindirectly and the magnitude of the momentum sustained is compared witha predetermined maximum value beyond which the fastener has to be openedor released to avoid a fracture, wound or like injury or hurt.

According to another characterizing feature of the invention saidunlocking means comprise a pyrotechnical charge and ignition means forfiring said charge when the integral is higher than said maximum value.

Thus is obtained a release or opening of the fastener much quicker thanby means of a mechanical opening system for instance of thespring-loaded or resiliently biased type.

The invention relates further to a method of automatically unlocking asafety fastener upon the occurrence or under the action of predeterminedcritical extraneous influences, comprising the steps of sensing ordetecting and measuring at least one force applied to at least oneelement of the fastener and comparing this measured force to apredetermined least or minimum value, said method being characterized inthat it also consists in integrating the force with respect to time,comparing the magnitude of the integral with a predetermined maximumvalue, automatically resetting the integral when said force is lowerthan a predetermined minimum value and automatically unlocking said fastener when the integral in case of a force higher than that minimumvalue is above said predetermined maximum value.

Owing to the invention a safety fastener is thus unlocked only when theintegral of a force, i.e. the momentum, is higher than a predeterminedmaximum value for a force above a predetermined minimum value, i.e. thefastener will be unlocked automatically for a constant or steadymagnitude of momentum, whether a very violent, strong or heavy or a veryfierce effort is involved or an effort of average, mean or mediumstrength extending in time as for instance in the case ofa slow twist oflarge amplitude, i.e. a torsion of large extent proceeding slowly intime.

According to a further characterizing feature of the method of theinvention the fastener is unlocked by firing or igniting a pyrotechnicalcharge. Thereby is available a power source enabling to unlock thefastener almost instantaneously and which delivers or supplies a verysignificant amount of energy for a device of very small bulk and weight.

The invention will be better understood and further objects,characterizing features, details and advantages thereof will appear moreclearly as the following ex planatory description proceeds withreference to the accompanying drawings given by way of non-limitingexample only illustrating various forms of embodiment of the inventionand wherein:

FIG. 1 diagrammatically shows an electric circuit of a system forreleasing a safety fastener according to the invention;

FIG. 2 diagrammatically shows an alternative embodiment or modificationof the system depicted in FIG. 1;

FIGS. 3 and 4 show in more detail parts of the circuit depicted in FIG.2;

FIG. 5 diagrammatically shows a graphical chart with curves illustratingthe variations of the force and momcntum sensed by a release systemaccording to the invention and plotted against or as a function of time;

FIGS. 6 and 7 diagrammatically show as block diagrams alternativeembodiments of the electrical circuits of the release arrangementsaccording to the invention;

FIG. 8 is a fragmentary perspective view of a safety fastener accordingto the invention fitted as a binding on a ski;

FIG. 9 is a top view of the rear part or back portion of the bindingshown in FIG. 8',

FIG. I is a view in longitudinal section of the portion of the bindingshown in FIG. 9',

FIG. 11 is a top view of the front portion of the binding shown in FIG.8;

FIG. I2 is a view in longitudinal section of the portion of bindingshown in FIG. II;

FIG. 13 is a top view of an alternative embodiment of the rear portionof a ski-binding according to the invention;

FIG. 14 is a view in longitudinal section of the portion of bindingshown in FIG. 13',

FIG. 15 is a top view of another alternative embodiment of a rearportion of a ski-binding according to the invention;

FIG. 16 is a view in longitudinal section of the portion of bindingshown in FIG. 15;

FIG. 17 is a top view of still another modification of a rear portion ofa ski-binding according to the invention; and

FIG. 18 is a view in longitudinal section of the back part of thebinding shown in FIG. 17.

There has thus been shown in the drawings and more particularly in FIG.I an electrical circuit of the means for releasing a safety fastenersuch as a ski-binding which embodies the process according to theinvention.

As already stated this process consists in sensing or detecting andmeasuring at least one force applied onto at least one element of thefastener and then integrating this force with respect to time. comparingthe magnitude or strength of the force to a predetermined mini mumvalue, automatically resetting the integral when the force is lower thanthe predetermined minimum value, comparing the magnitude of the integralto a predetermined maximum value and unlocking the fastener when theintegral is higher than the predetermined maximum value for a forceabove the predetermined minimum value.

The circuit embodying this method therefore comprises means for sensingor detecting and measuring at least one force applied to one element ofthe fastener. these sensing and measuring means including for instancestrain gauges l adhesively glued or stuck onto a deformable element ofthe fastener and for example connected in bridging relationship betweenthe ground 2 and a supply voltage a. The output of these sensing andmeasuring means is connected to the input of am plifying means Acomprising for instance a pair of series connected operationalamplifiers 3 and 4 the output of which is connected through an absolutevalue setting circuit ABS to integrating means I.

The absolute value setting circuit ABS comprises an operationalamplifier 5 the negative input of which is connected to the output ofthe amplifying means A and the positive input of which is connected tothe ground 2. The output of the operational amplifier 5 is connected tothe anode of a diode 7 and to the cathode of a diode 8. The negativeinput of the operational ampli fier S is connected through a resistor R,to the anode of the diode 8 and through a resistor R to the cathode ofthe diode 7. A resistor R connects the cathode of the diode 7 to thenegative input of a second operational amplifier 6 the positive input ofwhich is connected to the anode of the diode 8. A capacitor and aresistor are connected in parallel between the negative input of theoperational amplifier 6 and the output of the latter.

The integrating means I comprise an operational amplifier 9 the negativeinput of which is connected to the output of the operational amplifier6, and a resistor R and a capacitor C. are connected in parallel betweenthe negative input and the output of the operational amplifier 9. Thepositive input of the latter is connected to the ground 2 through aresistor. The drain b and the source a of a field effect transistor T,are mounted across a capacitor C, as shown. The gate of this fieldeffect transistor T is connected through a diode I0 to the output of anoperational amplifier II the positive input of which is connected to theoutput of said operational amplifier 6 and the negative input of whichis connected through a resistor to the intermediate point of a variableresistor R mounted between the ground 2 and a negative voltage supplyVa. The intermediate point of the variable resistor R defines togetherwith the ground 2 a reference voltage Vrn which corresponds to thepredetermined minimum threshold value of the force.

The variable resistor R the operational amplifier II and the fieldeffect transistor T thus define means for comparing the sensed signalwith a predetermined least or minimum value for resetting theintegrating means when the sensed signal is lower than the predeterminedminimum value as will be set forth hereinafter more in detail.

The output of the operational amplifier 9 is connected to the positiveinput of an operational amlifier 12 the negative input of which isconnected through a resistor to the intermediate point of a variableresistor R mounted between the ground 2 and the positive voltage supply+Va. The output of the operational amplifier I2 is connected to thetrigger-gate of a thyristor T the anode of which is connected to thepositive voltage supply +Va and the cathode of which is connectedthrough a pyrotechnical device 15 to the negative voltage supply Va. Acapacitor C, is connected in parallel between the negative voltagesupply Va and the anode of thyristor T Thus the operational amplifier 12and the variable resistor R form the means for comparing the signalintegral to a predermined maximum value V which is defined between theground and the intermediate point of the variable resistor R and thethyristor T the pyrotechnical device 15 and the capacitor C form themeans for unlocking the fastener which are operated when the signalintegral exceeds the predetermined maximum value as will be explainedhereinafter more in detail.

This release system operates in the following manner:

The strain gauges I will be assumed to be adhesively glued or stuck oneither side of a thin strip or lamination deformable through bending orflexure in either direction. The signal obtained at the output of thebridge-like connection arrangement of the strain gauges I is highlyamplified by the operational amplificrs 3 and 4 and then processed bythe absolute value setting circuit ABS which enables to obtain from theoutput of the operational amplifier 6 a signal having always the samesign whatever the positive or negative polarity of the output signalfrom the operational amplifier 4 may be. This output signal V from theoperational amplifier 6 is fed or applied on the one hand to thenegative input of the operational amplifier 9 of the integrating means Iand on the other hand to the positive input of the operational amplifier11 wherein it is compared with the reference voltage Vm corresponding tothe predetermined minimum value of the effort. When the voltage V whichhas the same sign as the voltage Vm is lower than that voltage Vm theoutput of the operational amplifier 11 has a potential substantiallyequal to +Va so that the field effect transistor T is turned on orbecomes conducting and the integration capacitor C is dischargingsteadily. There is thus provided in this case an automatic resetting ofthe integration means I.

On the contrary when the voltage V is higher than Vm, the potential atthe output of the operation amplifier 1] becomes equal to Va therebyresulting in turning off the field effect transistor T so that theintegration capacitor C can no longer discharge. There is thenintegration ofthe signal V within the integrating means I. The signal VIappearing at the output of the operational amplifier 9 is then fed tothe positive input of the operational amplifier 12 where it is comparedto the reference voltage V When the signal VI is lower than the voltageV the voltage of the operational amplifier 12 is substantially equal toVa, so that the thyristor T is turned off or non-conducting. When on thecontrary the voltage VI becomes higher than V the potential at theoutput of the operational amplifier 12 is substantially equal to +Va andthe thyristor T is turned on or becomes conductive thereby causing atthe same time the capacitor C to discharge into the pyrotechnical devicel5 and the unlocking of the fastener to take place.

an illustrative example of the shapes of the curves V and VI plottedagainst the time I has been shown in FIG. 5. It may be seen that at thetime t,. the voltage V is below the threshold Vm so that the voltage VIis zero; between t, and t the voltage V is higher than Vm and there isan integration but VI remains below V Between t and t the voltage V isbelow Vm thereby annulling VI and then between and t the voltage V ishigher than Vm and an integration takes place until the time t, at whichVI reaches the value V thereby causing the fastener to be unlocked. Itis assumed that the fastener has been locked again some time afterrelease thereof and that the voltage V then varies while remaining lowerthan Vm until the time After a time later than i V is higher Vm andvaries slowly. There is integration from and the voltage Vl increasesregularly up to V which it reaches at the time thereby causing thefastener to be unlocked.

In the first embodiment of the release system shown in FIG. I,operational amplifiers have been used which offer the advantage of beingperfectly symmetrical so that the different causes of drift of thecomponents as a function of temperature for example are compensating orbalancing by themselves.

An alternative embodiment of this circuit is shown in FIGS. 2 to 4.

In these Figures the means for sensing and transducing the effortapplied to the leg or foot of the ski-runner comprise a strain gauge Iconnected between the ground 2 and a dc. voltage source 20 through aresistor. An operational amplifier A amplifies the measure signalcorresponding to the sensed effort and feeds same to a high pass filterF consisting of a capacitor C coupled to the output of the operationalamplifier A and a pair of resistors connecting the terminals of thecapacitor C to the ground. The output of the filter F is connected to anintegrating circuit comprising an operational amplifier A, the input ofwhich is connected to the output of filter F and the other input ofwhich is connected to the ground 2 as well as a capacitor C connectedbetween the first input and the output of the operational amplifier A Acircuit I3 for comparing the value of the integral to a predeterminedmaximum value and for firing or igniting the pyrotechnical device 21 isconnected between the ground 2 and the output of the operationalamplifier A A circuit B for comparing the magnitude of the signalobtained at the output of the operational amplifier A with apredetermined critical minimum value is also connected between theoutput of the operational amplifier A and the ground 2 and receives thesignal from the output of the amplifier A These circuits B and B areshown more in detail in FIGS. 3 and 4, respectively.

The circuit B consists essentially ofa Schmitt trigger circuitconsisting of NPN-type transistors T and T respectively, theinterconnected emitters of which are biased to a predetermined value bydividing means constituted by two resistors P and P this predeterminedvalue corresponding to the maximum value set for the magnitude of theintegral of the measured effort. The capacitor C, has been shownconnected in broken lines between the input of this circuit B and theground 2 as the first aforesaid input of the operational amplifier Acorresponds to a fictive ground since in operation the operationalamplifier A has a nearly infinite voltage gain. The capacitor C, maytherefore be considered as connected between the ground and the input ofcircuit B The input of the circuit B is connected to the base of thetransistor T the collector of which is connected through a resistor tothe base of the transistor T Between the collector of the latter and thesource of direct current 20 is connected a relay 22 comprising anormally open contact 23. The making or closing of this contact 23results in the closing or completing of a supply circuit feeding awinding 24 connected between the direct current source 20 and the groundand which forms the primary winding of a transformer the secondarywinding of which consists for instance of another winding 25 fullyembedded in a blasting cap or primer 26 made from detonating materialsuch as explosive powder forming together with the winding 25 saidpyrotechnical device 21. The winding 25 may be closed on itself orcomprise a spark gap 27 allowing the firing or igniting of the charge 26by priming or flashover through field effect.

The circuit B shown in detail in FIG. 4 essentially comprises a Schmitttrigger circuit consisting of two PNP-type transistors T and T theinterconnected emitters of which are biased to a predetermined value forinstance by means of dividing means P P this predetermined valuecorresponding to the minimum lower value set for the measured effort. Aspreviously the connection arrangement of the capacitor C of theintegrating circuit has been shown in broken lines between the ground 2and the collector of transistor T connected to the output of theoperational amplifier A The Schmitt trigger circuit consisting of thetransistors T and T is used for operating by means of the transistor Tthe discharge of the integrating capacitor C when the measured effortbecomes lower than the predetermined minimum value.

The operation of this circuit shown in FIGS. 2 to 4 is the following:

An effort is sensed and measured by the strain gauge 1 and thenamplified by the operational amplifier A The filter F provided at theoutput of the operational amplifier A, enables to remove the directcurrent component from the amplified signal. An integration of thissignal with respect to time is achieved by means of the amplifier A andthe capacitor C The output signal from the amplifier A which correspondsto the integral of the measured effort with respect to time andaccordingly to the momentum is applied to the base of the transistor Twhich is therefore turned off as long as this signal is below thebiasing voltage of the transistors T and T Under such conditions thetransistor T is conducting, the relay 22 is for instance engerized andthe contact 23 is open. When the output signal from A is higher than thebiasing voltage of the transistors T and T, the transistor T becomesconducting or is turned on and the transistor T is turned off therebycausing the relay 22 to rest and closing the contact 23. The primarywinding 24 is then energized and causes the charge 26 to be firedthrough induction within the secondary winding 25 and priming throughfield effect by means of the spark gap 27.

At the same time the circuit B is driven by the signal V from the outputof the amplifier A,. As long as this signal V is higher than the biasingvoltage of the transistors T and T the transistor T remains turned offand the transistor T, is conducting. As soon as the signal V becomeslower than the bias voltage of these two transistors, the transistor Tbecomes conducting or is turned on and the transistor T is turned off.Then there appears a voltage step on the resistance of the collector ofthe transistor T this step being applied to the base of the transistor Tand rendering the latter conducting or turning same on. The capacitor Cis then discharge into the collector-emitter space of the transistor Tand the resetting of the integration circuit is thereby achieved.

At the outputs of the operational amplifiers A and A are thereforeobtained the same kind of curves as those shown in FIG. 5.

It should be pointed out that in the circuit shown in FIG. 1, it is veryeasy to change the values Vm V representing the predetermined minimumvalue of the effort and the predetermined maximum value of the integral,only be adjusting the variable resistors R and R,,. In the circuit shownin FIGS. 2 to 4, it is also possible to provide circuits or plug-inelectronic components for the purpose of adjusting the bias voltages ofthe transistors T and T, on the one hand and T and T on the other handand therefore to impart various values to the lower limit of the signaland to the upper limit of the integral.

In FIGS. 6 and 7 there is diagrammatically shown as block diagrams twoalternative embodiments of the release systems according to theinvention which enable to sense and to measure two efforts applied tothe leg or foot of the ski-runne r, such for instance as a twistingeffort and a tensile or pulling effort.

In FIG. 6, each effort E F is sensed and measured separately by means30, 31 respectively, and the output signal from these means 30, 31 isthen fed to the input of amplifying means 32, 33, respectively. Theoutput signal from the amplifying means 32 is fed to means 34 forcomparison to a predetermined minimum value and for resettingintegrating means 35 the input of which is also connected to the outputof the amplifiying means 32. The output of the integrating means 35 isconnected tothe input of means 36 for comparing the integral with apredetermined upper value and the output of the means 36 is itselfconnected to the input of the unlocking means 37.

Likewise the output of the amplifying means 33 is connected to the inputof means 38 for comparison of the signal with a predetermined minimumvalue and for resetting integrating means 39 the input of which is alsoconnected to the output of the amplifying means 33. The output of theintegrating means 39 is connected to means 40 for comparing the integralwith a predetermined maximum value, the output of the comparator means40 being connected to the input of the unlocking means 37.

In FIG. 7, both efforts F and F are sensed and amplified separately bythe means 30 and 32, and 31 and 33, respectively. The outputs of theamplifier means 32 and 33 are connected each one to an input of a mixingcircuit 41 the output of which is connected to the input of means 42 forcomparing the signal to a predetermined minimum value and for resettingintegrating means 43 the input of which is also connected to the outputof the mixing circuit 41. As previously, the output of the integratingmeans 43 is connected to unlocking means through the medium of means 44for comparing the integral with a predetermined maximum value. In thisform of embodiment of FIG. 7, the output signal from the mixing circuit41 corresponds to a combination of the output signals from theamplifying means 32 and 33, and this combination may be linear forinstance.

It should be noted that the unlocking means 37, 45 used in thealternative embodiments of FIGS. 6 and 7 may be py rotechnical devicescomprising a blasting cap or primer made from detonating material suchas explosive powder, of the kind shown in FIG. 3, of they may be of themagnetic ally operated type and comprise for instance a magnetic orelectro-magnetic circuit the magnetic saturation or desaturation ofwhich causes the fastener to be unlocked by exerting a pulling orrepelling force upon a fastener locking element.

In FIGS. 8 to 18 there has been shown various forms of embodiment of askibinding according to the invention.

This ski-binding the general lay-out of which is shown in FIG. 8 isfitted onto a ski and comprises a front stop member or abutment 51adapted to engage and to hold the toe of the boot of the ski-runner anda rear stop member or back abutment 51 adapted to engage and to hold orgrip the heel portion of the boot of the ski-runner.

The front stop member or abutment grip 51 as shown more in detail inFIGS. 11 and 12 is rotatably mounted about a vertical pivot 53 integralwith the ski 50. The front end of this stop member 51 is made integralor fast with one end 50 of a bending strip or flexing blade 55 which isarranged lengthwise in a vertical plane at right angles to the plane ofthe ski 50. The end 54 of the bending strip 55 is for instance forcefitted and held in a vertical slot ofthe front end ofthe stop member 51.The opposite end 56 of the bending strip 55 is guided in a verticallongitudinal slot 57 ofa part 58 while being kept bearing against a pairof vertical projections 59 of the inner walls of the slot 57. The part58 is movable longitudinally on the ski 50 with respect to the strip 55by means of a pivot 60 the bottom end of which carries an eccentricsnug, pin or stub 61 which extends into a hole of a supporting plate 62made fast with the ski 50. The member 58 is guided when travellinglengthwise between two raised or upturned flanges 63 of the plate 62.Thus through rotation of the pivot 60 it is possible to displace themember 58 longitudinally with respect to the bending strip 55 andtherefore to increase or decrease that portion of the strip 55 whichlies between the projections 59 and the front stop member 51. Thedeformation of the strip 55 through bending which is caused by theswinging of the front stop member 51 about the pivot pin 53, is sensedor detected by means of strain gauges 64 adhesively bonded onto bothmajor faces or large sides of the strip 55. These strain gauges 64 areconnected by conductors or like lead wires 65 to the electrical releasesystem diagrammatically shown as a block 66 behind or at the rear of thebinding.

Likewise the rear portion of the binding which is shown in greaterdetail in FIGS. 9 and 10 comprises a bending strip or flexing blade 70on both faces or large sides of which are adhesively bonded straingauges 71 connected to the electric release system 66. The rear end ofthe strip 70 is bearing upon an abutment 72 adjustable in position withrespect to the end of the strip 70 the other end of which is integralwith a clevis-like or yoke-shaped portion 73 comprising a pair ofupstanding side cheeks between which the rear stop member 52 ispivotally connected about a horizontal transverse pin 74. Theyoke-shaped part 73 is in turn pivotally connected about a horizontaltransvers pin 75 located ahead of the pin 74 between two legs or tabs ofa stationary part 76 secured to the ski 50 and carrying for instance theabutment 72.

The yoke-shaped part 73 also carries at its upper portion a horizontaltransverse pin 77 about which is pivotally fitted an arm 78 the upperportion of which may co-operate with a lever 79 also pivotally connectedabout the pin 77 and the lower portion of which is pivotally connectedonto one end of an arm 80 the other end of which is pivotally connectedto the rear stop member 52.

The yoke-shaped part 73 also carries a pyrotechnicai actuating device 81which is mounted in screw threaded engaging relationship into a screwthreaded portion of the part 73 and which is connected through aconductor or like lead wire 82 to the electric release system 66. Thispyroteehnical actuating device 81 is of a type known per se and itcomprises a charge of detonating material such as explosive powderaccommodated or housed inside of a cylinder which also contains a pistonthe rod 82 of which extends forward and out of the device 81. Ininoperative position the rod 82 assumes the position shown in FIG. 10and also forms a rest or bearing for the arms 78 and 80 in the lockedposition of the binding.

It should be noted that the part 73 extends forward with a plate 83adapted to lie under the heel of the boot of the ski-runner which whenthe binding is locked is held against motion between the plate 83 and ajaw 84 secured to the rear stop member 52. The position in height of thejaw 84 in relation to the stop member 52 is adjustable so that it may beadapted to boots of various sizes.

The operation of this rear portion of the binding is the following:

It should at first be assumed that the binding is locked on the boot ofthe ski'runner as shown in FIG. 10. When the ski-runner is for instancefalling forward a pulling effort T is exerted upon the rear stop member52 as shown in FIG. 10. This rear stop member 52 is locked in positionwith respect to the part 73 by means of the arms 78 and 80 which alsoserve to transmit the effort T to the part 73. The latter is thereforeswung clockwise as seen in FIG. 10 about its pivot pin and it causes theflexing strip 70 to be bent downwards The strain gauges 71 record adeformation or distorsion which is processed by the electrical system 66in the manner previously described. When the integral of the detectedsignal becomes higher than a predetermined maximum value for a signalhigher than a predetermined minimum value, the electrical system 66initiates the firing of the actuating device 81 so that the piston rod82 is moved forward and carries along or drives the arms and 78 duringits motion. The rear stop member 52 is then raised or lifted upwards andis disengaged from or releases the boot of the ski-runner.

Advantageously, the piston rod 82 may be kept in its forward or frontend position as long as the charge of detonating material of theactuating device 81 has not been replaced. It is thus impossible to lockagain the binding onto the boot of the ski-runner as long as theactuating device 81 has not been reset or brought back to operatingcondition. When this has been effected it suffices to pull the end ofthe lever 70 upwards for moving the arms 78 and 80 back to an alignedregistering condition in the position shown in FIG. 10 hence forclamping the rear stop member 52 onto the heel of the boot of theski-runner.

It should likewise be noted that the unlocking of the binding by meansof the actuating device 81 may also be operated from an effort exertedupon the front stop member 51, said effort being sensed by the straingauges 64 and transmitted to the electric system 66. The latter mayadvantageously be of the type shown in FIG. 6 or in FIG. 7.

An alternative embodiment of the rear portion of the binding as shown inFIGS. 13 and 14 and differs from the embodiment shown in FIGS. 9 and 10by the shape of the locking lever and of the rear stop member. in FIGS.13 and 14, the rear stop member 85 is as before pivotally connectedabout a pivot shaft 86 secured to a yoke-shaped or clevis-like part 87comprising a backward extension 88 forming a bending strip provided withstrain gauges 89 and a forward extension 90 on which rests the heel ofthe boot of the ski-runner. A locking lever 91 is pivotally connected at92 onto the yoke-shaped part 87 and carries at its lower end a roller 93riding on a slanting ramp or track provided by the rear stop or gripmember 85. The pyrotechnical actuating device 81 is as before carried bythe yoke-shaped part 87 and the piston rod 82 forms in normal positionthereof an abutment or rest for the locking lever 91. When the device 91is operated the piston rod 82 moves the lever 91 forward thereby freeingthe rear stop or grip member 85 and therefore unlocking the binding.When the device 81 is again in operative con dition or working order itis possible by means of the lever 91 to lock the rear stop or gripmember 85 onto the heel of the boot of the ski-runner as shown in FIG.

FIGS. and 16 illustrated another alternative embodiment of the rearportion of the binding which enables a selfacting locking of the bindingwhen the skirunner is inserting his boot into the binding. Thisalternative embodiment comprises as the preceding ones a yoke-shapedpart 95 formed with a backward extension 96 constituting a bending stripon which are mounted strain gauges 97 and with a forward extension 98adapted to be located under the heel of the boot of the ski-runner. Therear stop member or grip 99 is pivotally connected about a horizontaltransverse shaft 100 of a second yoke-shaped or clevis-like part 101pivotally connected into the first yoke-shaped part 95 about ahorizontal transverse pin 102. This part 101 supports a pyrotechnicalactuating device 81 like those described in the preceding forms ofembodiment. The piston rod 82 of the device 81 forms a rest or bearingfor a part 103 mounted for rotation about a pin 104 secured to the part101 and which is provided with a drawback or return spring 105 urging itback towards the actuating device 81. This part 103 forms a cam forlocking the rear stop member or grip 99 onto the heel of the boot of theski-runner by hearing with its upper end against a backward extension106 of the rear stop member or grip 99. A locking lever 107 is pivotallyconnected at its end portion to the yokeshaped part 85 and extends withits front end underneath the heel of the boot of the ski-runner as shownin FIG. 16. In its middle portion this lever 107 comprises an elongatedhole 108 forming a guide slot for a horizontal transverse pin 109secured to the yoke-shaped part 101. The yokeshapcd part 95 and 101 areconnected at their upper portions by a knuckle-joint or toggle-lever 110consisting of a pair of pivotally interconnected lever arms 111 and 112which are pivotally connected at their opposite ends. respectively, tothe part 101 and to the part 95. It should also be noted that the rearstop member or grip 99 is provided with a drawback or return spring 113urging it to swing back in the counterclockwise direction as seen inFIG. 16.

The operation of this alternative embodiment of the rear portion of thebinding is the following:

When the binding is unlocked, the yoke-shaped portion 101 has swung inthe clockwise direction in relation to the part 95 about its shaft 102,the locking part 103 has rocked or tilted about its shaft 104 in thedirection opposite or away from the device 81 and the rear stop memberor grip 99 has slightly rotated in the clockwise direction under theaction of the drawback spring 113. Owing to the swinging ofthe part 101about the shaft 102, the front portion of the lever 107 has beenslightly lifted or raised. When the ski-runner inserts his boot into thebinding. he presses with the heel onto the front end of the lever 107thereby swinging the part 101 in the counterclockwise direction aboutthe shaft 102 and causing the rear stop member or grip 99 to be lockedonto the heel of the boot. The rear stop member or grip 99 is kept inposition by the locking part 103. The lever arms 11] and 112 are then inaligned or substantially registering position as shown in FIG. 16 andare fully locking the binding.

In case of release through the electrical system 66, the piston rod 82is caused to push the locking part 103 against the action of thedrawback spring thereby disengaging the rear stop member or grip 99 andallowing same to swing about the shaft 100 under the action of thedrawback spring 113. The boot ofthc ski-runner is then frccd.

Another alternative embodiment of the rear stop member or grip of thebinding is shown in FIGS.17 and 18, the difference consistingessentially in using a pyrotechnical actuating devicee 115 which acts nolonger for driving the piston rod towards the forawrd portion of thebinding but on the contrary for pulling backwards the piston rod 116which is pivoted through a ball-and-socket joint 117 onto a lever 118for locking the rear stop member 119. This rear stop member or grip 119is pivotally connected about a horizontal transverse shaft 120 onto ayoke-shaped part 121 also pivotally connected about the pin 120 onto apart 122 secured to the ski 50. The part 122 supports the pyrotechnicaldevice 115 as well as a pin 123 for pivotal connection of the lockinglever 118. A drawback spring 124 tends to swing the lever 118 about theshaft 123 in the clockwise direction in FIG. 18. The rear stop member ongrip 119 extends backwards of a locking lever 125 and is urged to swingback in the counterclockwise direction about the shaft 120 by a biasingspring 126.

Advantageously the lever 118 comprises a shoulder 127 which in thelocked position of the binding bears or presses onto the upper edge ofthe rear stop member or grip 119 for keeping same locked onto the heelof the boot of the ski-runner.

The operation of this alternative embodiment is the following:

When the electrical release system aetuates the device 115, the pistonrod 116 is pulled backwards of the binding and carries along in itsmotion the lever 118 in rotation about the shaft 123 in thecounterclockwise direction. The rear stop member or grip 119 is thendisengaged from the shoulder 127 and under the action of the drawbackspring 126 it swings about the shaft 120 in the counter-clockwisedirection for freeing the heel of the boot of the ski-runner. Afterputting the actuation device 115 again into working order, the rear stopmember or grip 119 may be caused to bear upon the heel of the boot ofthe ski-runner as shown in FIG. 18 while exerting an upward pull uponthe end of the lever 125. Under the action of its return spring 124 thelever 118 is then pushed against the rear stop member or grip 119 andwhen the latter moves down below the level of the shoulder 127 thisshoulder is locking same in a position holding the boot against motion.

It should be noted that many proximity sensors or displacement detectorsmay be used for sensing and measuring the efforts applied to an elementof the binding instead of the strain gauges previously described. it ispossible indeed to use for instance strain gauges with round wire orpellicular weft or grating, vacuumdeposited strain gauges.semi-conductive strain gauges, strain gauges with stretched wire.capacitive sensors or gauges, inductive proximity displacement gauges orwith plunger cores and differential transformer gauges or sensors.

In some cases. the ski-binding which has been described maybe simplifiedby having a locking brittle element which is broken by the actuation ofthe pyrotechnical device and then unlocks this ski-binding.

The invention is not at all limited to the forms of embodiment describedand shown which have been given by way of example only. In particular itcomprises all the technical equivalents of the means described and shownas well as their combinations if the latter are carried out according toits gist and used within the scope of the appended claims.

What is claimed is:

1. An automatically operable safety fastener operated under control ofextraneous influences, comprising means for sensing and transducing intoan electrical signal at least one force applied to at least one elementof the fastener, first comparison means for comparing the electricalsignal so derived with a predetermined minimal value, means connected tosaid first comparison means for integrating with respect to time saidtransduced signal to provide an integrated signal output only when themagnitude of the transduced signal is larger than said predeterminedminimal value, second comparison means for comparing said integratedsignal with a predetermined maximum value, and fastener unlocking meansactuated only when the magnitude of said integrated signal is greaterthan the magnitude of said predetermined maximum value.

2. A fastener according to claim 1, wherein said integrated signal isequal to zero when the magnitude of the transduced signal is less thansaid predetermined minimum value, and wherein said unlocking meanscomprise a pyrotechnical charge, and means for firing said charge whensaid integrated signal is higher than said maximum value.

3. A fastener according to claim 2, wherein said charge comprises ablasting cap with detonating material such as explosive powder in whichis embedded an electrically conducting winding forming the secondary ofa transformer the primary winding of which consists of anotherelectrically conducting winding of said firing means, an electriccurrent being adapted to flow through said primary winding under controlof said extraneous influence to fire said charge through induction.

4. A fastener according to claim 3, wherein said winding embedded insaid blasting cap with detonating material comprises a spark gapenabling to fire said charge by priming through field effect.

5. A fastener according to claim 3, wherein said winding is closed onitself and enables to tire said charge through heating by Joule effect.

6. A fastener according to claim 1, wherein said unlocking meanscomprise a circuit including a pyrotechnical charge, a capacitor andmeans for completing said circuit such as a thyristor enabling saidcapacitor to discharge into said circuit when said signal integralexceeds said predeten'nined maximum value.

7. A fastener according to claim 1, wherein said unlocking meanscomprise magnetic or electromagnetic locking circuits and means forsaturating or desaturating said circuits when said integral is higherthan said predetermined maximum value.

8. A fastener according to claim 1, comprising at least two assemblieseach consisting of said sensing and transducing, integrating, firstsignal comparing and second comparing means, said unlocking means beingconnected to each assembly actuated when at least one of said integratedsignals is higher than the corresponding maximum value.

9. A fastener according to claim 1, wherein said sensing and transducingmeans provide at least two different signals each corresponding to aforce applied to an element of said fastener, said signals beingprocessed by a mixing circuit before being fed to said integrating andfirst comparing means.

10. A fastener according to claim 1, wherein said sensing andtransducing means comprise displacement sensors selected from the groupincluding inductive gauges, capacitive gauges, strain gauges, connectedto amplifying means such as operational amplifiers.

11. A fastener according to claim 1, wherein said sensing andtransducing means comprise strain gauge sensors mounted in bridgeconnection and connected to operational amplifiers the output signal ofwhich is transmitted to said integrating and comparing means through anabsolute value setting circuit.

12. A fastener according to claim 11, wherein said integrator meanscomprise an operational amplifier the input of which is connected to theoutput of said absolute value setting circuit and a capacitor connectedin parallel between said input and said output of the operationalamplifier.

13. A fastener according to claim 12, wherein said first comparisonmeans comprise a field efiect transistor the drain and the source ofwhich are connected across said integrating capacitor and the triggergate of which is connected to the output of an operational amplifier theinput of which is connected to the output of said absolute value settingcircuit and the other input of which is fed with a reference voltagecorresponding to said minimum value.

14. A fastener according to claim 11, wherein said second comparisonmeans comprise an operational amplifier the input of which is fed withthe output signal from said integrator means and the other input ofwhich is fed with a reference voltage corresponding to saidpredetermined maximum value whereas the output of which is connected tosaid unlocking means.

15. A fastener according to claim 1, wherein said integrator meanscomprise a high pass filter for removing the direct current component ofsaid signal delivered from said transducing means and an operationalamplifier including an input resistor and a capacitor connected inparallel across said operational amplifier.

16. A fastener according to claim 1, wherein said second comparisonmeans comprise a first Schmitt trigger circuit with two transistors theinterconnected emitters of which are biased to a voltage ofpredetermined magnitude corresponding to said predetermined maximumvalue and a relay operating a contact for actuating said unlockingmeans, said contact closing as soon as said integral exceeds saidpredetermined maximum value.

17. A fastener according to claim 16, wherein said first comparisonmeans comprise a second Schmitt trigger circuit with two transistors theinterconnected emitters of which are biased to a voltage ofpredetermined magnitude corresponding to said minimum value and a thirdtransistor controlled by said Schmitt trigger circuit and enabling todischarge the capacitor of said integrating means to the ground whensaid signal is lower than said minimum value and to reset saidintegrating means.

18. A fastener according to claim 1, forming a safety ski-bindingcomprising a front stop member movable about a pivot extending at rightangles to the plane of said ski and a rear stop member which is mountedfor being movable about a transverse pivot extending in parallelrelation to said plane of said ski and which is adapted to lock the bootof the ski-runner within said binding. wherein said sensing andtransdueing means cooperate with at least one bending strip one end ofwhich, at least in the binding locking position, is made rigidly fastwith at least one of said front and rear stop members and the other endof which rests on at least one bearing pointv 19. A fastener accordingto claim [8, wherein said sensing and transducing means comprise straingauges adhesively bonded or secured onto at least one side face of saidbending strip.

20. A fastener according to claim [8, wherein one of said bending stripsis arranged in lengthwise vertical position with respect to said skiwhile being constantly fast through one end with said front stop memberand having its other end guided in a longitudinal slot of a partadjustable in longitudinal position on said ski and which is hearingagainst a pair of opposite projections integral with the inner walls ofsaid slot.

21. A fastener according to claim 18, wherein said pivot of said rearstop member is secured to a part movable about a transverse pinextending in parallel relation to the plane of said ski. said partcomprising at one end a plate adapted to lie underneath the heel of theboot of the ski-runner and at its other end an extension forming one ofsaid bending strips, which extends in longitudinal parallel relation tothe plane of said ski whereas its free end is bearing upon a projectionintegral with said ski.

22. A fastener according to claim 21, wherein said movable part carriessaid pyrotechnical device actuated by said fastener unlocking means andincluding a pyrotechnical charge housed in a cylinder also containing apiston the free end of which outside said piston is adapted to act uponmeans for locking said rear stop member so as to release same andtherefore to disen gage the boot of said ski-runner from saidski-binding.

23. A method of automatically unlocking a safety fastener upon theoccurrence or under the action of predetermined critical extraneousinfluences, comprising the steps of sensing and measuring at least oneforce applied to at least one element of said fastener and comparingsaid measured force with a predetermined minimum value, wherein theimprovement consists in that said method also comprises the steps ofintegrating said force with respect to time to provide an integratedforce greater than zero only when the measured force exceeds saidpredetermined minimum value. said integrated force being equal to zerofor all values of the measures force less than the minimum value. comparing the magnitude of said integrated force with a predetermined maximumvalue, and automatically unlocking said fastener when said integratedforce, for a measured force higher than said minimum value, becomeshigher than said predetermined maximum value.

24. A method according to claim 23, comprising the step of unlockingsaid fastener by firing a pyrotechnical charge.

25. A method according to claim 23, consisting in unlocking saidfastener by magnctical saturation or desaturation of a fastener lockingmagnetic or electromagnetic circuit.

26. A method according to claim 23, comprising the steps of measuring atleast two forces acting upon elements of said fasteners, processing saidforces by comparing each one of them with a predetermined minimum value,by integrating and comparing each integral with a predetermined maximumvalue, and unlocking said fastener when at least one of said integralsbecomes higher than the corresponding maximum value for a correspondingforce above the corresponding minimum value.

27. A method according to claim 23, comprising the step of measuring atleast two forces acting upon elements of said fastener, combining saidforces into a resulting force, processing said resulting force bycomparing it with a predetermined minimum value, by integrating it, bycomparing said integral with a predetermined maximum value and unlockingsaid fastener when said integral of the resulting force becomes higherthan said maximum value for a resulting force above said minimum value,the integral of said resulting force being zero for all values of saidresulting force below said predetermined minimum value.

i t t Notice of Adverse Decision in Interference In Interference No.99,759, involving Patent No. 3,919,563, D. J. Lautier, L. L. Maeder andP. E. Mayer, CONTROLLABLY SELF-RELEASABLE SAFETY FASTENER AND METHOD OFUNLOCKING SAME, final judgment adverse to the petentees was renderedApr. 10, 1980, as to claims 7, 9, 11-14, 25 and 27.

[Oflicial Gazette July 92, 1.980.]

1. An automatically operable safety fastener operated under control ofextraneous influences, comprising means for sensing and transducing intoan electrical signal at least one force applied to at least one elementof the fastener, first comparison means for comparing the electricalsignal so derived with a predetermined minimal value, means connected tosaid first comparison means for integrating with respect to time saidtransduced signal to provide an integrated signal output only when themagnitude of the transduced signal is larger than said predeterminedminimal value, second comparison means for comparing said integratedsignal with a predetermined maximum value, and fastener unlocking meansactuated only when the magnitude of said integrated signal is greaterthan the magnitude of said predetermined maximum value.
 2. A fasteneraccording to claim 1, wherein said integrated signal is equal to zerowhen the magnitude of the transduced signal is less than saidpredetermined minimum value, and wherein said unlocking means comprise apyrotechnical charge, and means for firing said charge when saidintegrated signal is higher than said maximum value.
 3. A fasteneraccording to claim 2, wherein said charge comprises a blasting cap withdetonating material such as explosive powder in which is embedded anelectrically conducting winding forming the secondary of a transformerthe primary winding of which consists of another electrically conductingwinding of said firing means, an electric current being adapted to flowthrough said primary winding under control of said extraneous influenceto fire said charge through induction.
 4. A fastener according to claim3, wherein said winding embedded in said blasting cap with detonatingmaterial comprises a spark gap enabling to fire said charge by primingthrough field effect.
 5. A fastener according to claim 3, wherein saidwinding is closed on itself and enables to fire said charge throughheating by Joule effect.
 6. A fastener according to claim 1, whereinsaid unlocking means comprise a circuit including a pyrotechnicalcharge, a capacitor and means for completing said circuit such as athyristor enabling said capacitor to discharge into said circuit whensaid signal integral exceeds said predetermined maximum value.
 7. Afastener according to claim 1, wherein said unlocking means comprisemagnetic or electromagnetic locking circuits and means for saturating ordesaturating said circuits when said integral is higher than saidpredetermined maximum value.
 8. A fastener according to claim 1,comprising at least two assemblies each consisting of said sensing andtransducing, integrating, first signal comparing and second comparingmeans, said unlocking means being connected to each assembly actuatedwhen at least one of said integrated signals is higher than thecorresponding maximum value.
 9. A fastener according to claim 1, whereinsaid sensing and transducing means provide at least two differentsignals each corresponding to a force applied to an element of saidfastener, said signals being processed by a mixing circuit before beingfed to said integrating and first comparing means.
 10. A fasteneraccording to claim 1, wherein said sensing and transducing meanscomprise displacement sensors selected from the group includinginductive gauges, capacitive gauges, strain gauges, connected toamplifying means such as operational amplifiers.
 11. A fasteneraccording to claim 1, wherein said sensing and transducing meanscomprise strain gauge sensors mounted in bridge connection and connectedto operational amplifiers the output signal of which is transmitted tosaid integrating and comparing means through an absolute value settingcircuit.
 12. A fastener according to claim 11, wherein said integratormeans comprise an operational amplifier the input Of which is connectedto the output of said absolute value setting circuit and a capacitorconnected in parallel between said input and said output of theoperational amplifier.
 13. A fastener according to claim 12, whereinsaid first comparison means comprise a field effect transistor the drainand the source of which are connected across said integrating capacitorand the trigger gate of which is connected to the output of anoperational amplifier the input of which is connected to the output ofsaid absolute value setting circuit and the other input of which is fedwith a reference voltage corresponding to said minimum value.
 14. Afastener according to claim 11, wherein said second comparison meanscomprise an operational amplifier the input of which is fed with theoutput signal from said integrator means and the other input of which isfed with a reference voltage corresponding to said predetermined maximumvalue whereas the output of which is connected to said unlocking means.15. A fastener according to claim 1, wherein said integrator meanscomprise a high pass filter for removing the direct current component ofsaid signal delivered from said transducing means and an operationalamplifier including an input resistor and a capacitor connected inparallel across said operational amplifier.
 16. A fastener according toclaim 1, wherein said second comparison means comprise a first Schmitttrigger circuit with two transistors the interconnected emitters ofwhich are biased to a voltage of predetermined magnitude correspondingto said predetermined maximum value and a relay operating a contact foractuating said unlocking means, said contact closing as soon as saidintegral exceeds said predetermined maximum value.
 17. A fasteneraccording to claim 16, wherein said first comparison means comprise asecond Schmitt trigger circuit with two transistors the interconnectedemitters of which are biased to a voltage of predetermined magnitudecorresponding to said minimum value and a third transistor controlled bysaid Schmitt trigger circuit and enabling to discharge the capacitor ofsaid integrating means to the ground when said signal is lower than saidminimum value and to reset said integrating means.
 18. A fasteneraccording to claim 1, forming a safety ski-binding comprising a frontstop member movable about a pivot extending at right angles to the planeof said ski and a rear stop member which is mounted for being movableabout a transverse pivot extending in parallel relation to said plane ofsaid ski and which is adapted to lock the boot of the ski-runner withinsaid binding, wherein said sensing and transducing means cooperate withat least one bending strip one end of which, at least in the bindinglocking position, is made rigidly fast with at least one of said frontand rear stop members and the other end of which rests on at least onebearing point.
 19. A fastener according to claim 18, wherein saidsensing and transducing means comprise strain gauges adhesively bondedor secured onto at least one side face of said bending strip.
 20. Afastener according to claim 18, wherein one of said bending strips isarranged in lengthwise vertical position with respect to said ski whilebeing constantly fast through one end with said front stop member andhaving its other end guided in a longitudinal slot of a part adjustablein longitudinal position on said ski and which is bearing against a pairof opposite projections integral with the inner walls of said slot. 21.A fastener according to claim 18, wherein said pivot of said rear stopmember is secured to a part movable about a transverse pin extending inparallel relation to the plane of said ski, said part comprising at oneend a plate adapted to lie underneath the heel of the boot of theski-runner and at its other end an extension forming one of said bendingstrips, which extends in longitudinal parallel relation to the plane ofsaid ski whereas its free end is bearing upon a prOjection integral withsaid ski.
 22. A fastener according to claim 21, wherein said movablepart carries said pyrotechnical device actuated by said fastenerunlocking means and including a pyrotechnical charge housed in acylinder also containing a piston the free end of which outside saidpiston is adapted to act upon means for locking said rear stop member soas to release same and therefore to disengage the boot of saidski-runner from said ski-binding.
 23. A method of automaticallyunlocking a safety fastener upon the occurrence or under the action ofpredetermined critical extraneous influences, comprising the steps ofsensing and measuring at least one force applied to at least one elementof said fastener and comparing said measured force with a predeterminedminimum value, wherein the improvement consists in that said method alsocomprises the steps of integrating said force with respect to time toprovide an integrated force greater than zero only when the measuredforce exceeds said predetermined minimum value, said integrated forcebeing equal to zero for all values of the measures force less than theminimum value, comparing the magnitude of said integrated force with apredetermined maximum value, and automatically unlocking said fastenerwhen said integrated force, for a measured force higher than saidminimum value, becomes higher than said predetermined maximum value. 24.A method according to claim 23, comprising the step of unlocking saidfastener by firing a pyrotechnical charge.
 25. A method according toclaim 23, consisting in unlocking said fastener by magnetical saturationor desaturation of a fastener locking magnetic or electro-magneticcircuit.
 26. A method according to claim 23, comprising the steps ofmeasuring at least two forces acting upon elements of said fasteners,processing said forces by comparing each one of them with apredetermined minimum value, by integrating and comparing each integralwith a predetermined maximum value, and unlocking said fastener when atleast one of said integrals becomes higher than the correspondingmaximum value for a corresponding force above the corresponding minimumvalue.
 27. A method according to claim 23, comprising the step ofmeasuring at least two forces acting upon elements of said fastener,combining said forces into a resulting force, processing said resultingforce by comparing it with a predetermined minimum value, by integratingit, by comparing said integral with a predetermined maximum value andunlocking said fastener when said integral of the resulting forcebecomes higher than said maximum value for a resulting force above saidminimum value, the integral of said resulting force being zero for allvalues of said resulting force below said predetermined minimum value.